let head = [1, 2, 3, 4, 5]
function ListNode(val) {
    this.val = val;
    this.next = null;
}
function a(list) {
    let head = new ListNode(0)
    let cur = head
    for (let i = 0; i < list.length; i++) {
        cur.next = new ListNode(list[i])
        cur = cur.next
    }
    return head.next
}
var reverseList = function (head) {

};



Array.prototype.my_map = function (callback) {
    const newArr = []
    for (let i = 0; i < this.length; i++) {
        newArr.push(callback(this[i], i, arr))
    }
    return newArr
}